Portion of a light bulb



FIG. 1 is a left view showing a first embodiment of my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a right view thereof;

FIG. 6 is a left perspective view thereof;

FIG. 7 is a left view showing a second embodiment of my new design;

FIG. 8 is a front view thereof;

FIG. 9 is a rear view thereof;

FIG. 10 is a bottom view thereof;

FIG. 11 is a right view thereof;

FIG. 12 is a left perspective view thereof;

FIG. 13 is a left view showing a third embodiment of my new design;

FIG. 14 is a front view thereof;

FIG. 15 is a rear view thereof;

FIG. 16 is a bottom view thereof;

FIG. 17 is a right view thereof; and,

FIG. 18 is a left perspective view thereof.

The broken lines shown on the drawings are for the purpose of illustration and form no part of the claimed design. 

CLAIM The ornamental design for a portion of a light bulb, as shown and described. 